1. Field of the Invention
This invention relates to a motion converting system and, more particularly, to a drive shaft driven at a constant rotational velocity, a driven shaft rotatable in response to the rotation of the drive shaft and coupling mechanisms to vary the rotational position between the drive and driven shafts to generate pressure and motion as a function of the rotational position of the shafts.
2. Description of the Background Art
A linear actuator, sometimes called a positive control actuator, is a device consisting of a piston reciprocable in a cylinder from one end to the other. By providing operating fluid under pressure to one end of the cylinder or the other, the piston can be made to move in one direction or the other in response to the introduction of the pressurized fluid. The movement of the piston can thus be used for creating a mechanical motion in response to the flow of the fluid.
The efficiency of a linear actuator can be increased, in terms of pressure and response time, by increasing the pressure to the ends of the cylinder to the highest pressure desired for a particular application. In such circumstances, however, unusually strong distribution lines would be required and a safety hazard to personnel would be encountered since, for example, a pin-hole leak in a 5,000 p.s.i. line could inject a lethal quantity of hydraulic fluid through a person's skin.
With the advanced technology of electrical motors, there has been an effort to revive electrical actuators as substitutes for the more common hydraulic actuators. Because of their mechanical characteristics, however, it is extremely difficult to get smooth operation and positive positioning of the controlled item through electric actuators.
Hydraulic actuators provide many benefits over electrical actuators. They are, however, generally deficient in that no convenient technique is known for converting the output of a driving motor into a hydraulic output for driving a linear actuator wherein the hydraulic output is readily variable without varying the rotational speed of the driving motor and the fluid is not heated through constant circulation.
The system of the present invention and its mechanism for variably driving a linear actuator with a constant velocity motor was developed in response to the need to improve the efficiency of linear actuators.
Various approaches are disclosed in the patent literature for driving linear actuators and for converting a constant rotational speed motor into variable pressure outputs. By way of example, U.S. Pat. No. 2,508,315 to Van Weenen discloses a hot gas motor whose phase between a piston and displacer changes as the phase angle between two crank shafts changes. Movement of a lever imparts an axial movement of shaft 16 causing the two crank shafts to perform unequal rotary motions due to the particular construction of the gear wheels. This patent is concerned with controlling a Stirling engine through the change of phase position of the driving and driven pistons through spiral gears. The present invention is not directed to a Stirling engine nor does it rely on spiral gears.
The Wallis patent, U.S. Pat. No. 3,482,457, employs a planetary-type phase changing device and moves a valve element in either direction to control the fluid pressure between two lines. Due to the fluid pressure, several motors impart motion upon tracks thereby turning the pinion. This then turns a sun-type gear causing the speeds of a displacer crank shaft and power crank shaft to change relative to each other. This operation causes a phase change between the power and displacer mechanism and thus the output power at the engine's power crankshaft. A significant difference between the Wallis patent and the present invention is that Wallis relies upon a sun-type gear to change the relationship of the driving and driven crank shafts.
In the Vos patent, U.S. Pat. No. 4,357,799, there is disclosed a hot gas reciprocating machine in which the relative phase of the pistons can be adjusted by adjusting two shafts. The adjustment is controlled by a motor which moves a piston causing an arm to move. Another arm, which is fixedly attached to the first arm, must move, thereby turning two shafts by the rotation of associated gears. The Vos patent, unlike the present invention, is directed to a Stirling engine control.
In U.S. Pat. No. 4,395,880 to Berchowitz, another Stirling engine is disclosed with a gearing method employed to change the relative phase of a four-piston system. A pair of shafts are moved axially in the same direction causing gears to rotate in opposite directions thereby rotating the crank pins, also in opposite directions. This changes the phase angle between each pair of thermodynamically coupled pistons. The Berchowitz Stirling engine is controlled through changing angle relationships between the driven and driving crank shafts. This is significantly different from the gear train of the present invention. The first six figures of Berchowitz depict a spiral gear to change relationships, while FIG. 7 employs a sun-type gear similar to that disclosed in the Wallsi patent discussed above.
Lastly, U.S. Pat. No. 4,228,656 to MacGlashan and 4,392,350 to Marks are also of interest. MacGlashan relates to the control of a hot gas engine through changing the phase relationship between the driving and driven crank shafts. Marks relates to a cam operated piston totally unsuitable for the pump configuration of the present invention. The essence of Marks, unlike the present invention, is to provide control for a Stirling engine by changing the phase of the driving and driven cylinders.
As illustrated by the great number of prior patents and commercial devices, efforts are continuously being made in an attempt to improve linear actuators and control mechanisms therefor. Such efforts are being made to render linear actuators and their drives more efficient, reliable, inexpensive and convenient to use. None of these previous efforts, however, provide the benefits attendant with the present invention. Additionally, prior patents and commercial devices do not suggest the present inventive combination of component elements arranged and configured as disclosed herein. The present invention achieves its intended purposes, objects and advantages through a new, useful and unobvious combination of component elements, with the use of a minimum number of functioning parts, at a reasonable or lower cost to manufacture, and by emplying only readily available materials.
Therefore, it is an object of the present invention to provide an improved system for converting the output of a constant speed motor to variable fluidic pressure at the ends of a linear actuator comprising a drive gear coupled with an electric motor for concurrent rotation at a fixed rotational speed; a driven gear operatively coupled to the drive gear; a drive train operable in response to rotation of the drive gear to rotate the driven gear, the gear train including adjustment mechanisms for selectively varying the rotational orientation between the drive and driven gears; a pump having a pair of spaced cylinders in axial alignment with pistons coupled through a reciprocal connecting shaft and with a connector rod pinned at its midpoint to the connecting shaft for oscillation; rigid links coupling the ends of the connector rod with the drive and driven gears so that rotation of the drive and driven gears will oscillate the connecting rod and reciprocate the connecting shaft at a speed correlated to the orientation of the adjustment mechanisms of the gear train; and fluidic lines coupling the outputs of the cylinders to the ends of a linear actuator so that adjustment of the gear train will vary the output of the pump to vary the fluidic flow from zero to maximum and a constant pressure to control the speed of the linear actuator.
It is a further object of the present invention to drive linear actuators from a variable volume fluidic source.
It is a further object of the present invention to convert the output of a constant speed motor into a variable volume output.
It is a further object of the present invention to adjust the rotational position of a gear train for converting the output of a drive motor into a variable volume feed while maintaining the drive motor at a constant rotational velocity.
The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.